Art of refining mineral hydrocarbon oils



Patented Mar. 22, 1938 ART OF REFINING MINERAL HYDRO- CARBON OILS Arthur L. Lyman, Berkeley, Calif., assignor to Standard Oil Company of California,

San

Francisco, Calif., a corporation of Delaware 7 No Drawing. Application March 25, 1933,

Serial No. 662,832

11 Claims.

This invention relates to an improved process for refining of mineral hydrocarbon oils, and has particular reference to a method of separating crude petroleum or its distillates into fractions or components of different chemical composition, whereby oils of relatively high viscosity index may be obtained from crude oils or their distillates normally characterized by an inferior viscosity-temperature relationship or a low viscosity index.

As is well known, lubricating oils from Pennsylvania crudes have higher viscosity indices (as the term viscosity index is defined by Dean and Davis in Chemical Metallurgical Engineering, 1929, volume 36, pages 618-9) than those oils obtained from Mid-Continent, Gulf, or California crudes. l i

It is a purpose of this invention to provide a method of extracting from such low viscosity in- 20 dex oils, wholly or in part, those hydrocarbons responsible for this inferiority (generally understood to be of aromatic and/or naphthenic molecular structure), thus providing oils consisting wholly or largely of those hydrocarbons characterized by high viscosity indices (generally understood to be of paraflinic molecular structure). It is a further object of this invention to provide a method of selective solvent refining which may be carried out at ordinary temperatures, whereby either refrigeration or the maintenance of high temperatures during the treatment are avoided, and to provide solvents for such a process that may be recovered at relatively low temperatures for reuse.

Aniline is known to provide excellent solvent refinement of the type here described (see, for example, U. 5. Letters 'Patent 1,741,555, issued December 31, 1929 to Chappell and Ziser). Refinement with aniline is possible at ordinary temperatures; in additionto this advantage in commercial refining operations aniline vaporizes at a relatively low temperature, and hence may be completely recovered from the hydrocarbons associated with it, whether in the railinate. or in the extract, at relatively low temperatures.

It has now been found that a combination solvent, comprising aniline in combination with one or more of a considerable number of relatively low boiling organic liquids, efiects a very marked improvement over the selective solvent refinement to be obtained by the use of aniline alone. These low boiling organic liquids, whose use in combination with aniline is exemplified more fully hereinbelow, are all characterized by their miscibility with aniline at the temperatures of (c1. sm-13) treatment and by their complete miscibility with the hydrocarbon'oils to be treated over a wide range of temperatures, including those of treatment. Being miscible with mineral hydrocarbon oils in all proportions over a wide range of temperatures, including those of treatment, these organic liquids are not to be considered as selective refining solvents in themselves, and their use in selective solvent refining treatment is not contemplated except in conjunction with aniline.

As examples of liquids contemplated for use in conjunction with aniline in the process of this invention, benzene, toluene, the xylenes, ethylene dichloride, normal and secondary butyl alcohols, secondary butyl acetate, amyl alcohols and the like may be mentioned. Petroleum ether or Similar volatile petroleum distillates, or other low boiling organic liquids which are not miscible with aniline at the temperatures of treatment, are mere diluents of the hydrocarbonoil to be selectively extracted, and do not function to pro-- vide the benefits obtainable in the practice of the invention. In general, any organic liquid which is miscible with the oil to be refined and which is also miscible with aniline, at the temperatures of the refinement, and which may be separated by ordinary volatilization processes from both the rafiinate and the extract resulting from the refinement, satisfies all of the requirements for use with aniline in the practice of this invention.

The following examples will illustrate the nature of the invention and the character of the results obtained by its practice:

A Kettleman Hills (California) crude lubricating oil distillate was treated with 400 volume percent of a mixture of 75% aniline and 25% benzol, in one dump. After thorough agitation and stratification, both operations being carried out at ordinary temperatures, 40.5 volume percent of raffinate was separated. This raffinate was dewaxed; the characteristics of the refined, de- Waxed oil, in comparison with those of the original crude distillate when similarl y dewalxed, were as follows:

A second 400 volume percent dump of the 75 aniline25 benzol solvent mixture was applied to a part of this once treated oil, before dewaxing. After extraction and dewaxing a refined oil in 27.5% yield (on the basis of the original distillate) was obtained, with the following characteristics:

Vis. at 692 Vis. at 283 Vis. at 210 69 Viscosity index 81 The tabulation below provides a comparison between the refinement obtained by the use of aniline alone and of aniline plus be-nzol; in addition, there is included a treatment wherein a diluent was used, which is miscible with the petroleum oil, but immiscible with aniline (petroleum ether), and hence not embraced within the process of the invention.

300 vol.

300 vol. per- Ori inal 300 vol. cent aniline distilpercent +100 V01 100 vol. late, deaniline, Meant percent petr.

waxed dewaxed genzol ether, dc-

dewaxed Waxed Vol. percent yield 67. 2 46. 4 59. 8 Vis. 100 F 2800 1150 875 1167 803 422 337 422 104 79 74 79 Vis. index 5 53 71 51 dichloride, each treatment being in two equal dumps. The following results were obtained:

The process I as exemplified above has been described as making use of combinations of aniline and an aniline-miscible and oil-miscible organic liquid in the proportions of 3 parts aniline to 1 part suitable combination liquid. It will be understood that these proportions are described herein only to exemplify the results obtained with various combination solvents, in comparison with each other and with aniline alone, and that these proportions may be varied over a considerable range. In general, as the ratio of the second component to aniline increases in the combination solvent mixture,'the yield of rafiinate decreases, the viscosity index of the raffinate increases, and a less selective separation of hydrocarbons of difierent molecular structure is effected. This ratio obviously approaches a point where there is noseparation obtainable by reason of the mutual miscibility of the solvent mixture and the petroleum distillate. Certain variations will be found in the effectiveness of any certain combination due to the character of the hydrocarbons in various crude petroleum stocks, as is exemplified above in similar treatments on two widely different California crude petroleum stocks. i

Treatments in one or in a number of solvent applications are embraced within the scope of the process, as obvious advantage is to be obtained in the use of small successive applications, rather than a single large application.

Certain low boiling organic liquids which may be effective in solvent extraction of the type here described may be difficult to recover from 300 volt; 300 V01; percen percen 300 vol. aniline aniline cent Original P- distillate amllno 100 vol; 100 volt; 100 701 percent percen percen N-BuOH 11 1311011 OHCI'OHOI The above treatments were carried out on a dewaxed Kettleman ,Hills (California) crude lubricating oil distillate; the total amount of solvent shown was applied in two equal successive dumps, with stratification and removal of extracted material between dumps. All treatments were carried out at atmospheric temperature.

As will be observed, the liquids whose use is here exemplified are all miscible both with aniline and with the petroleum oil to be extracted, at the temperatures of the treatment.

Further: A Mid-way (California) crude lubricating distillate was treated with volume percent aniline alone and with 200 volume percent of a mixture of 75% aniline and 25% ethylene the rafiinate or from the extract by reason of chemical reactivity with aniline at super-atmospheric temperatures. An example of such an otherwise suitable liquid is ethylene dichloride, which, while of great effectiveness in solvent refining proper, as exemplified above, reacts with aniline at the super-atmospheric temperatures which would ordinarily be used for recovery of the solvent mixture for reuse. The several other liquids whose use in combination with aniline is exemplified above (benzol, normal and secondary butyl alcohol), as well as many others not specifically exemplified ,(as toluene, the xylenes, 'butyl acetate, the amyl alcohols, and the like, embraced within the limits of the invention),

are easily recoverable from both the rafiinate and the extract, for reuse, by volatilization in the ordinary manner.

Obviously the oil-miscible, aniline-miscible liquid may be admixed with the oil to be treated and the aniline separately added to the admixture thereafter, if this procedure is more convenient than that exemplified above: the results of the treatment are identical whether the oil-miscible, aniline-miscible liquid is added to the oil to be treated or to the aniline.

While I have described in detail numerous illustrative examples of the practice of any process and of the results specifically obtained therefrom, I have done so by Way of illustration only and with the intention that nolimitation should be imposed upon the invention thereby.

I claim:

1. In the art of refining mineral hydrocarbon oils, the process which comprises separating an oil containing parafiinic and high boiling aromatic and naphthenic hydrocarbons into fractions respectively richer in paraifinic and in high boiling aromatic and naphthenic compounds by simultaneously extracting said oil with aniline and with an organic liquid miscible with aniline and miscible with the said oil, said organic liquid being further characterized in allowing formation of said extracted fraction into a separate liquid phase.

2. A process of treating mineral oils characterized by a high content of high boiling aromatic and naphthenie hydrocarbons, comprising agitating the oil with aniline and with an organic liquid miscible With aniline and with the said oil, allowing said mixture to form an oil layer and an aniline layer, and separating the oil layer from the aniline layer.

3. In the art of refining mineral oils characterized by a high content of high boiling aromatic and naphthenic hydrocarbons, the process which comprises extracting said oil with a mixture of aniline and benzol.

4. In the art of refining mineral oils, the process which comprises extracting said oil with a mixture of aniline and a butyl alcohol.

5. In the art of refining mineral oils, the process Which comprises extracting said oil with a mixture of aniline and butyl acetate.

6. In the art of refining mineral hydrocarbon oils, the process which comprises separating an oil containing paraffinic and high boiling aromatic and naphthenic hydrocarbons into fractions respectively richer in paraflinic and in aromatic and naphthenic compounds by simultaneously extracting said oil, at atmospheric tem-' peratures, with aniline and with an organic liquid miscible with aniline and miscible with said oil, said organic liquid being further characterized in allowing formation of said extracted fraction into a separate liquid phase.

7. In the art of refining mineral hydrocarbon oils, the process which comprises separating an oil containing parafiinic and high boiling aromatic and naphthenic hydrocarbons into fractions respectively richer in paramnic and in aromatic and naphthenic compounds by simultaneously extracting said oil with aniline and with an organic liquid which is miscible with aniline, miscible with said oil and which has a boiling point range not included within the boiling point ranges of said paraifinic, aromatic and naphthenic fractions, said organic liquid being further characterized in allowing formation of said extracted fraction into a separate liquid phase.

8. In the art of refining mineral oils, the process which comprises simultaneously extracting said oil with about 3010 volume percent of aniline and about 100 volume percent of benzol.

9. In the art of refining mineral oils charac-- terized by the presence of large amounts of high boiling aromatic and naphthenic constituents, the process which comprises extracting said oil at atmospheric temperatures with a mixture of aniline and benzol.

10. In the art of refining mineral oils with selective solvents, the process which consists in extracting said oil with a mixture of aniline and an organic liquid miscible with aniline and miscible with said oil, said organic liquid also being characterized by allowing formation of the extracted fraction into a separate liquid phase, separating the diiferent liquid phases, and removing the aniline and said organic liquid from the oil fractions.

11. In the process of refining mineral oils comprising separating said oils into fractions respectively richer in paraflinic and in aromatic and naphthenic compounds, the step of extracting with aniline in the presence of an organic liquid miscible with aniline and miscible with said oil, said liquid being selected from the group consisting of benzene, toluene, the xylenes, ethylene dichloride, normal and secondary butyl alcohols, secondary butyl acetate and amyl alcohols, whereby the viscosity index of the rafiinate is increased.

ARTHUR L. LYMAN. 

